The waste products of the manufacture of lindane consist essentially of isomeric hexachlorocyclohexanes. They are obtained in significant amounts in addition to the desired .gamma.-isomer. Recovery of the starting materials, benzene and chlorine, is therefore of great importance. It is known that the 1,2,3,4,5,6-hexachlorocyclohexane isomers (HCH isomers) can be reacted with zinc dust in aqueous suspension to form benzene and zinc chloride [Chem. Abstr. 46 (1952), 3962 e; 48 (1954), 2096 ab]. However, satisfactory degrees of reaction are obtained only if they are mixed thoroughly for a long time, since two solid phases have to react with each other and the resulting third phase (zinc chloride) has to be dissolved by the water in order to prevent a blockage of the reaction surfaces. Because of these complicated heterogenous reaction conditions, the reaction of larger quantities is, very expensive. The use of alcohols, for example methanol, for dissolving the organic substrate is likewise known [Chem. Abstr. 47 (1953), 5906 b; 46 (1952), 3962 e]; however, very large amounts of zinc are required, and the processing is more difficult.
It is also known to recover zinc from zinc chloride by electrolysis.